This View helper returns a CSH (context sensitive help) button with an icon.
It enables you to include hints into backend forms.

TYPO3 uses this functionality all over the backend, and it is noticeable by the small “question mark” image when hovering
over the element, whilst clicking on the element displays the help text in a small tooltip.

There's a special case in which the “table” property doesn't need to be
defined. This is the case when there are form fields in the module, but when
there is no 1:1 column in the database. For example, in the Scheduler, which
stores its information in a serialized format in a single field, or in the case
of a search field, whose value isn't sent to the database. Such fields can be
assigned a csh icon through the addition of an entry in
ext_tables.php:

\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addLLrefForTCAdescr('_MOD_FullModuleName','Path to a language file');

Note the reference to the fully-formed module name. This is comprised of the
category (e.g. “web”), the upper-camel-cased extension name and the upper-
camel-cased module name. In the example of an extension named “sfextbase” and a
module named “extbase”, the complete name would be:

<trans-unitid="email.alttitle"xml:space="preserve"><source>Email</source></trans-unit><trans-unitid="email.description"xml:space="preserve"><source>Enter your email address</source></trans-unit><trans-unitid="email.details"xml:space="preserve"><source>
I am a really long description, which gives plenty of detail about
this field relating to an email address, as well as what you need to
note and that you need to add a valid email address in this field.
</source></trans-unit>